文件的上传与下载在我们的日常工作中十分的常见,在项目开发中也是经常要用到的,springmvc可以更好地支持文件的上传和下载;但是springmvc实现文件的上和下载需要配置一些东西;为了能够支持文件的上传,表单必须使用post方式提交;需要设置enctype属性
enctype="multipart/form-data" method="post"- 只有 enctype="multipart/form-data" 才支持文件的上传,表示是以二进制流的形式处理表单数据;
- application/x-www-form-urlencoded 是enctype 的默认值,只处理表单的 value属性的值;
- enctype="text/plain" 只会讲空格转换成为+号,其他东西不变,适合于邮件的发送;
实例:
采用二进制流的形式上传文件
1.首先创建一个新项目;在项目中进行导包;
导包是除了导入springmvc的包之外还要导入文件上传的包
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.3.3</version>
</dependency>2.创建 web.xml的配置文件;
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
id="WebApp_ID" version="3.0">
<servlet>
<servlet-name>springmvc</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:springmvc-servlet.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>springmvc</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
<!--配置过滤器-->
<filter>
<filter-name>myFilter</filter-name>
<!--<filter-class>com.kuang.filter.GenericEncodingFilter</filter-class>-->
<filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>utf-8</param-value>
</init-param>
</filter>
<!--/* 包括.jsp-->
<filter-mapping>
<filter-name>myFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
</web-app>3.创建springmvc的配置文件;
在配置spring-servlet.xml文件时注意将bean的id配置为 : multipartResolver ,不然会出现400 错误; 因为Springmvc在默认中没有配置MultipartResolver ,所以在默认中他不能处理文件的上传工作;
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc.xsd">
<context:component-scan base-package="com.zhang.controller"/>
<mvc:default-servlet-handler/>
<mvc:annotation-driven/>
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver" id="InternalResourceViewResolver">
<property name="prefix" value="/WEB-INF/jsp/"/>
<property name="suffix" value=".jsp"/>
</bean>
<!--ID必须为multipartResolver，否则就400问题-->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
<property name="defaultEncoding" value="utf-8"/>
<property name="maxUploadSize" value="1048576"/>
<property name="maxInMemorySize" value="40960"/>
</bean>
</beans>
4.创建一个前端页面:
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<body>
<form action="/upload" enctype="multipart/form-data" method="post">
<input type="file" name ="file"/><br>
<input type="submit" value="upload">
</form>
</body>
</html>
5.创建controller类;
- Controller实现,必须加上@RequestParam("file")接收文件,主要是用来实现类的分装;
- 接收文件类型需要设置为CommonsMultipartFile .
package com.zhang.controller;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.commons.CommonsMultipartFile;
import javax.servlet.http.HttpServletRequest;
import java.io.*;
@Controller
public class FileController {
@RequestMapping("/upload")
private String fileupload(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {
//获取文件名
String filename = file.getOriginalFilename();
if ("".equals(filename)){
return "redirect:/index.jsp";
}
System.out.println(filename);
//上传文件路径设置
String path = request.getServletContext().getRealPath("/upload");
File reapath = new File(path);
if (!reapath.exists()){
reapath.mkdir();
}
//读取写出
//获取文件输入流
InputStream ints = file.getInputStream();
//获取文件输出流
OutputStream outs = new FileOutputStream(new File(reapath,filename));
//写出文件
int len=0;
byte[] bytes = new byte[1024];
while ((len=ints.read(bytes))!=-1){
outs.write(bytes,0,len);
outs.flush();
}
outs.close();
ints.close();
return "redirect:/index.jsp";
}
}
6.进行测试;
测试完成后返回前端页面;就可以查看到上传的文件;
方式二:采用file.transferTo实现文件的上传
@RequestMapping("/upload")
@ResponseBody
public String upload(@RequestParam("file")CommonsMultipartFile file,HttpServletRequest request) throws IOException {
//上传文件的保存路径
File realPath = new File(request.getServletContext().getRealPath("/upload"));
if (!realPath.exists()){
realPath.mkdir();
}
//transferTo：将文件写入到磁盘，参数就是一个文件
file.transferTo(new File (realPath+"/"+file.getOriginalFilename()));
return "redirect:/index.jsp";
}测试完成;
文件的下载实现:
//文件的下载实现
/*
设置响应头
读取文件
写出文件
执行操作
关闭流
*/
@RequestMapping("/download")
public String download(HttpServletResponse response) throws IOException {
//要下载的文件的地址
String path="C:\\Users\\张沧\\Desktop";
String filename="5.jpg";
//设置响应头信息
//使页面不缓存
response.reset();
response.setCharacterEncoding("UTF-8");
response.setContentType("multipart/form-data");
response.setHeader("Conten-Disposition","attachment;filename="+ URLEncoder.encode(filename,"UTF-8"));
File file = new File(path, filename);
//输入输出流
FileInputStream inputStream = new FileInputStream(file);
ServletOutputStream outputStream = response.getOutputStream();
//执行操作
int len=0;
byte[] bytes = new byte[1024];
while ((len=inputStream.read(bytes))!=-1){
outputStream.write(bytes,0,len);
outputStream.flush();
}
outputStream.close();
inputStream.close();
return null;
}
创建前端页面代码;
<p><a href="${pageContext.request.contextPath}/download">下载图片</a></p>测试下载成功: